Impedance transformer network



Nov. 20, 1956 v. R. DE LONG IMPEDANCE TRANSFORMER NETWORK 2 SheetsSheet1 Original Filed April 26, 1951 IN VEN TOR.

"IA/CIA, 1?, flizawa Ar 7 a/P/ia r Nov. 20, 1956 v. R. DE LONG IMPEDANCETRANSFORMER NETWORK Origiqal Filed April 26, 1951 2 Sheets-Sheet 2INVENTOR. V/lvcz/vr R 0222 0N6 4 r r can/[r United States PatentIMPEDANCE TRANSFORB'IER NETWORK Vincent R. De Long, Cedar Rapids, Iowa,assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation ofIowa Original application April 26, 1951, Serial No. 223,090, now PatentNo. 2,669,698, dated February 16, 1954. Divided and this applicationOctober 6, 1952, Serial No. 313,243

3 Claims. (Cl. 333-32) This invention relates in general to impedancetransformers and in particular to inductance :coils wound and connectedso as to obtain a desired impedance transformation. This case is adivision of Serial Number 223,090, filed April 26, 1951, now Patent No.2,669,698, issued Feb. 16, 1954.

In the electrical field it is oftentimes desirable to make an impedancetransformation so that an output at one impedance may be connected to aninput with a different impedance. In order to prevent a discontinuityoccurring when such a connection is made, it is desirable to place inthe line an impedance transformer which will eliminate thediscontinuity. For a more complete discussion of the theory of matchingtransformers reference may be made to Patent 2,470,307, issued toGuanella on May 17, 1949, entitled High Frequency Matching Transformer.

Applicants invention constitutes an improvement in the manner of windingthe coil and a new manner of connecting coils so as to obtain differentimpedance ratios has been developed.

It is an object of this invention to provide an impedance transformer byutilizing two or more inductance coils of this invention.

Another object of this invention is to provide a COll with high surgeimpedance which has opposite sides of the line wound in the samedirection about a coil form while maintaining a relatively largedistance between the turns of one side of the line and the turns of theopposite side of the line.

Yet another object of this invention is to provide an improved highimpedance coil which has opposite sides of the line wound about it inthe same direction with relatively large spacing between turns of theopposite sides of the lines and with more than one turn of each sidemade between turns of the opposite line.

A feature of this invention is found in the provision for a new andnovel coil which may be connected in various manners to obtain differentimpedance transformations.

Further objects, features and advantages of this invention will becomeapparent from the following description and claims when read in view ofthe drawings, in which;

Figure 1 is an air view drawing of the coil of this invention;

Figure 2 illustrates a connection for making a 9-1 impedancetransformation; and,

Figure 3 illustrates a connection developed by applicant for making a9-1 impedance transformation.

With reference to Figure 1 a coil form, designated generally as 10, maybe made of ceramic material, for example, and has attached alongitudinal insulating strip 11 which might be formed of polystyrene,for example.

A pair of input terminals 12 and 13, respectively, pass through one endof the insulating strip 11 and fasten to the form to hold the insulatingstrip rigidly to it.

Output terminals 14 and 16, respectively, pass through the opposite endof strip 11 and attach to the coil form 10.

2,771,585 Patented Nov. 20, 1956 One side 17 of a line is attached toterminal 12. ductor 17 passes through a diagonal slot 18 formed in theinsulating strip 11 and is wound about the coil form to make a firstturn 19, passes over the insulating strip 11 in a slot 21 and makes asecond turn 22 about the form 10.

After the second turn 22 the conductor is received in a slot 23 formedin the insulating strip 1'1 and passes diagonally across the strip for asubstantial longitudinal distance from the second turn 22 and is woundabout the form to make a third turn 24. A fourth turn 26 is made aboutthe form 10 by crossing over the insulating strip 11.

After the fourth turn the conductor to output terminal 14 passesdiagonally along the strip 11.

The other side 27 of the line is connected to input terminal 13 andpasses under the insulating strip 11 through a diagonal slot formedtherein to emerge for a first turn 28. A second turn 29 is made byallowing the conductor to pass under the insulating strip 11 through aslot 31 formed therein. After turn 29 the conductor passes through atransverse slot 32 formed in the under side of the strip 11 and passes asubstantial distance down the strip 11 to emerge and make turn 33 whichis the third turn for the second conductor. A fourth turn 34 is made bythe second conductor. After the last turn 34 the second conductor isconnected to the output terminal 16.

The longitudinal spacing between opposite sides of the line increasesthe surge impedance of the coil and a practical size coil may beobtained. In other words, in order to get a relatively high surgeimpedance, a much smaller coil will be needed when wound as shown inFigure l than when the opposite sides of the line are spaced relativelyclose together.

An advantage obtained by spacing two turns of the same side of the lineclose together is to increase the surge impedance by increasing themutual inductance between adjoining turns of the same line.

A coil wound such as shown in Figure 1 has the characteristic that itoffers no impedance to balanced current flowing through the coil, but ahigh impedance to any unbalanced current. This is true because with abalanced current opposite sides of the line will carry equal andopposite current and the total inductance will be substantiallycancelled for the reason that the conductors are wound in the samedirection.

Unbalanced currents, however, flow in the same direction through bothsides of the line and the induct-ances would add and thus form a highimpedance path. As shown in the patent to Guanella, previouslyreferenced, impedance transformations may be made by connecting two ormore coils in the line. For example, Guanellas Figure 6 illustrates aconnection for two coils to obtain a 4-1 impedance transformation.

Applicants Figure 2 illustrates means for obtaining a 9-1 impedancetransformation between input terminals 3 6 and 37 and output terminals38 and 39. If the impedance of each coil is Z, the total impedancebetween the terminals 36 and 37 is 3Z. The rectangles 4'1, 42 and 43each represent coils with two coil sides or windings such as shown inFigure 1 and are connected as shown in applicants Figure 2 which is thesame as the right part of Figure 7 of the Guanella patent. Applicant hasdiscovered, however, that an impedance transformation of 9-1 may be madewith the connection as shown in Figure 3 with two coils 44 and 46. Thismay be shown by considering the unbalance currents represented by arrowsplaced adjacent the coils in Figure 2. It is to be seen that theunbalance current flowing in the middle coil 42 will be cancelled andtherefore, the coil 42 has no effect on the unbalanced currents.

This suggested to applicant that the coil 42 might be eliminated and theconnections made as shown in Figure 3.

Conv In this case input terminals 47 and 48 are connected to windings 52and 53, respectively, of coils 4'4 and 46. The opposite ends of windings52 and 53 are connected to output terminals 49 and 51. The secondwinding 57 of coil 4 '4 has its end adjacent the input terminal 47connected to output terminal 49 and its opposite end connected to outputterminal 51. The second winding 58 of coil 46 has its end adjacent theinput terminal 48 connected to the output terminal 51' and its oppositeend connected to the output terminal 49. With this connection theimpedance transformation is 9-1 but only two coils 44 and 46 are usedinstead of the three coils shown in Figure 2.

It is seen that this invention provides a new and novel way of winding acoil so as to obtain a high surge impedance and also provides a newconnection for two coils to obtain a 9-1' impedance transformation.

Although this invention has been described with respect to a preferredembodiment thereof, it is not to be so limited as changes andmodifications may be made therein which are within the full intendedscope of the invention as defined by the appended claims.

I claim:

1. An impedance transformer for obtaining a nine-tone impedancetransformation at high impedance levels comprising first and secondinductance coils, each coil including first and second input terminalsand first and second'output' terminals, each coil also having a pair ofseparate windings, with one of. said windings being connected betweenthe first input and output terminals, and the other of said windingsbeing connected between the second input and output terminals of therespective coil, each of said windings having two groups of turns woundin the same direction, two closely-wound turns forming each of saidgroups, with said groups being spaced widely apart relative to thespacing of the turns within a group, each coil having the groups of onewinding interleaved with the groups of its other winding in spacedrelationship, said transformer having first and second input points,with one input point connected to the first input terminal and thesecond output terminal of said first coil and to the first inputterminal of said second coil, the second input point being connected tothe second input terminal of said first coil and to the second inputterminal and the first output terminal of said second coil, and outputpoints for said transformer being provided by the first output terminalof said first coil and the second output terminal of said second coil.

2. An impedance transformer for obtaining a nine-toone impedancetransformation at relatively high imped- 4 l ance levels, comprisingfirst and second coils, each of said coils including first and secondinput terminals and first and second output terminals, each coil havingfirst and second windings, with each coil having its first windingconnected between its first input and first output terminals, and witheach coil having its second winding connected between its second inputand second output terminals, each winding formed with a plurality ofgroups of turns wound in the same direction, with each group includingat least two closely-spaced turns, the respective groups of the firstand second windings of each of said coils being axially interleaved, apair of input points for said transformer, with one input pointconnected to the first input terminal and second output terminal of saidfirst coil and to the first input terminal of said second coil, theother transformer input point being connected to the second inputterminal of said first coil and to the second input terminal and thefirst output terminal of said second coil, a pair of output points forsaid transformer being provided by the first output terminal of saidfirst coil and the second output terminal of said second coil.

3. A radio-frequency impedance-matching transformer providing anine-to-one ratio between a pair of input points and a pair of outputpoints comprising first and second coils, each of said coils havingfirst and second input terminals and first and second output terminals,each coil having a first winding connected between its first inputterminal and its first output terminal, and each coil also having asecond winding connected between itssecond inputterminal and its secodoutput terminal, with each winding formed with a plurality of groups ofcloselyspaced turns wound in the same direction, with said groups ofeach Winding being widely spaced from each other, and each coil havingthe groups of its first winding interleaved between the groups of itssecond winding, one transformer input point being connected to the firstinput ter-' minal of said second coil and to the first input terminaland the second output terminal of said first coil, with the secondtransformer input point being connected to the second input terminal ofsaid first coil and to the" first output terminal and second inputterminal of said second coil, and said transformer output points beingprovided by the first output terminal of said first coil and the secondoutput terminal of said second coil.

References Cited in the file of this patent UNITED STATES PATENTS2,470,307 Guanella May 17, 1949

